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Malicious use of grc.com

ShieldsUp(tm) is an application developed by Steve Gibson of Gibson
Research Corporation that allows a web user to request a remote port scan
of their local system via the GRC.Com web site
(https://grc.com/x/ne.dll?bh0bkyd2).
The "Probe my Ports" option performs a scan of many common tcp ports
and reports the status of each port back to the user's browser.

The development of the application and its method of identifying the
client IP address is quite insecure. As a result, ShieldsUp! allows the web
user to
perform a port scan against any other machine on the Internet and return the
results to the web user. The remote system will log the scan as having
originated from one of Steve Gibson's machines.

Gibson has chosen to use a simple hidden tag in the client-side HTML code
to identify the IP address that is passed to the scanning engine. Though
the client's IP address is hashed, it is trivial to alter the value of the
hidden tag in order to request that a different IP address be scanned. The
true IP address is never checked in the HTTP header during the scan -
ShieldsUp happily scans the other box while returning the result set into
the
browser of the box that requested the scan.

Fenris, The Wolf, a member of Hammer of God, quickly reviewed
the hash algorithm used to represent the IP address and found it weak;
therefore, one can easily submit requests, via the Shields Up web page,
for specific IP addresses to be scanned. These findings are not my own,
and I have not included the details of the hash here as it is used to
display a copyrighted page. The Wolf may post his findings if he chooses
to do so, but I will not make that choice for him.

Instead, we can easily bypass the need to crack the hash by simply using
the "IP Agent" supplied by Gibson. Over a year ago, a hacked version of IP
Agent was published that allowed one to supply an address to scan-- Gibson
discounted this as a non-issue, but reportedly fixed IP Agent to perform a
check to prevent this from happening.

However, IP Agent now supports multiple client IP addresses. One simply
needs to bind the targeted IP addresses to a local interface and perform a
scan request. In this case, ShieldsUp presents friendly command buttons
listing the IP addresses bound to the local interfaces and allows you to
select any one that you want scanned. Again, no other checking is done,
and ShieldsUp will scan whatever IP address you ask it to and display the
results in your own browser.

According to the scanning page, "Information gained will NOT be retained,
viewed, or used by us in any way for any purpose whatsoever" which
basically invites anyone to use Gibson's site to do port scans of other
people's boxes without fear of detection.

Additionally, multiple post requests can be easily scripted to perform
scans against a site in attempts to perform a denial of service attack
against a host. In these cases, with sufficient requests generated, one
could ask grc.com to attack another site and it will comply.

One would have hoped that instead of Mr. Gibson spending so much time
expounding on the theoretical DoS capabilities of Raw
Sockets, that he instead had used that time to properly develop his own
application in order to prevent the same. Those concerned with malicious
attacks from grc.com should block Gibson's netblock at the border.

GRC Issue

If anyone else is curious about this issue the mailing list is Vuln-Dev and you can subscribe to it at SecurityFocus.com

I've read a few of the arguments on Vuln-Dev about this issue and they generally fall into three categories:

1.) Those who believe that GRC is irresponsible and ridicules them for making such an “insecure” web system
2.) Those who believe that it is not a big risk, because there are hundreds of programs on the Internet that will do exactly what ShieldsUp does.
3.) Those who believe that it is not a big risk, because the IP address of the user is logged and therefore if ShieldsUp was used for malicious purpose than they could check the users IP.

Personally, I tend to side with arguments 2 & 3.
Not only because they are more logical, but because most of the arguments that fall into category 1, seem to be from vindictive people who just want to attack Steve Gibson because of his views on the raw socket & DoS issue.

Simon Templer

\"Your work is to discover your world and then with all your heart give yourself to it. \"
-The Buddha

Very interesting article. I know Steve has been getting a lot of flak recently, this does not help him. I thought the raw sockets <--> shields up being used as a DOS was pretty funny.

I don't know if port scanning is illegal here in the US or not. It would totally suck if it were. I mean, how would you check your own systems. Then again certain sexual acts are illegal in many places, I would have to treat the port scanning laws a bit like I treat those sexual acts laws. *.dumb_law >> /dev/null

I don't know about anyone else, but I wouldn't use ShieldsUP! to scan another PC. It only goes after half a dozen ports, which is pretty worthless, if you ask me. Maybe for the newbie user it's good (and that's who it's designed for), but for most technical types there's other scanners out there.

Personally, this is a non-issue to me. I get more port scan generated traffic in five minutes online at home than someone scanning me with shields up for an hour would generate.

Chris Shepherd
The Nelson-Shepherd cutoff: The point at which you realise someone is an idiot while trying to help them.
\"Well as far as the spelling, I speak fluently both your native languages. Do you even can try spell mine ?\" -- Failed Insult
Is your whole family retarded, or did they just catch it from you?